There are a few things I don't tell my partner, mostly because I'm not sure exactly what to say, or how to tell him. It's nothing bad. Mostly just deep hurt from past breakups, stuff to do with my family, and not wanting him to freak out by how much I want kids someday, etc, etc. Eventually, I will tell him everything that I can, but we're still working on things. I know there are also sides of one another we haven't gotten to see yet either!